This invention relates to apparatus for automatically purging the reservoir of a water recirculating system and, in particular, for draining and refilling the reservoir of an evaporative cooler.
Fluid systems wherein a working fluid, typically water, is continually recirculated during operation to a utilization means are typically exposed to and interact with the environment. This is particularly the case when the evaporative properties of the fluid are utilized to produce a cooling effect on a portion of the fluid itself or a second fluid in heat exchanging relation thereto. For example, the evaporative cooler commonplace in arid climates for cooling an air stream relies on a low humidity environment for successful operation. The cooler utilizes water saturated pads with air being drawn therethrough with the evaporation of a portion of the water cooling the circulated air.
In operation, the water is continually recirculated from a primary reservoir to a position above the pads from which it travels downward by gravitational effect to return to the reservoir. Since evaporation reduces the amount of water returned to the reservoir, make-up water is continually added to the reservoir to maintain it at a desired level. The contaminents in the water are for the most part not volatile so that the concentration of contaminants in the reservoir builds during continued operation leading to rusting, scaling and mineral deposition. These undesired effects shorten the maintenance cycle of the system and also reduce its operating life time.
The deleterious effects of mineral build-up can be significantly reduced by frequent and regular purging of the reservoir coupled with refilling it from the supply course which tends to reduce the impurity and mineral content departures from the baseline or supply source levels. In industrial fluid recirculating systems wherein selective loss of the working fluid takes place over a period of time, a series of valves and timers are normally provided to accomplish regular and automatic purging of the system reservoir. The larger scale units can include this additional equipment without significant incremental cost increases. However, the small application unit, typically the evaporative cooler used on single-family residences, is a relatively inexpensive unit and the addition of electrically operated valves and timers significantly add to the cost. Further, a cost-benefit analysis on the incorporation of such additional parts in evaporative coolers frequently leads to the conclusion that the addition of times or remote-actuated purge apparatus is not economically sound from a marketing standpoint.
At present, the typical user of an evaporative cooler relies on his own scheduled maintenance program to purge the reservoir of his water recirculation system. Since the apparatus is normally placed near the highest portion of the house, the periodic draining per schedule is frequently ignored with the dual consequences that the bottom rusts through within a few years while the mineral deposits adversely affect the pump and water intake valve. As an alternative, impurity gathering elements such as magnesium-containing blocks are often placed in the water to attract mineral impurities. These elements cause a precipitation of impurities thereby reducing the frequency between required draining operations. While evaporative coolers incorporating remotely-actuated valves for purging the reservoir are known, the valves have been found to become inoperable due to scale formation from mineral deposition over a period of time. Thus, the devices are unreliable and the owner of the evaporative cooler is unsure of the frequency of the purges since he frequently is not aware of the failure of the automated apparatus to function properly on a regular basis.
Several designs of automatic purge and refill apparatus for affixation to the base of existing coolers have been proposed. These units rely on the cessation of the operation of the pump coupled with the drain back of water within the circulation network to cause the water level to rise to the point where a siphon drain valve is primed to cause the reservoir to be evacuated. While the purging of the reservoir is accomplished, the evaporative cooler is rendered inoperative during the drain and refill cycle thereby requiring the user to forego the cooling effects of the apparatus for that period. This approach to automatic purging which renders the entire apparatus inoperable on a regular basis has not been favored by the user.
Accordingly, the present invention provides a means for automatic purging of the reservoir of a fluid circulating system which is operative without significantly disabling the operation of the circulation pump which continues to provide fluid to the utilization means during a major portion of the purging interval. Further, the invention is capable of being retrofitted into existing installations without altering the mounting of the structure.